Sound-reproducing amplifier



June 12, 1928 v A. H. GIBSON SOUND REPRODUCING AMPLIFIER Filed June 2, 1926 paicctnicrl inns ll-l,

iii iirsiti ANGUS H. GIB Olii', 0F SALT LAKE CITY. UTAH, ASSIGNGTH 130 AMERICAN RADIO PROD- UCI'S CQMIPANY, OF SALT LAKE CITY, U'Ilhiill. A CORTEOHATIQN 011i! UTAH.

SQ UND-IRIEIPH3DU SING A iT IF'LILEZEERi Applic-nticn fiicil 3mm 3,

This invrnlinn rclziL-cs to Stilllili-lfipl'i'l lillfi" ing amplifiers lpr use with. rzu'lic-rsceiving nmviiriilriisand isjiitriiihwl to provide 1 (lei ice cl? that class which shrill reproduce in full, loud tunes ihc nriginz l sounds trainsinitlieil vlvctrirnlly 11c thrapparatus wiihcut the usual loss nl ilistinciness or clam-mess clue to. distortion of the reproducing (levicc. In practice it has generally been found that with increasing lcurlncss in the sciinrls reproduced by radio transmission there is :1 loss of clistinctness 0r clcsrness chic to disiortion cf vibration in the reprcrlucing rlcvi This invention LiQZZiS with that; problem and is il'rtenclcd tc provide a device of that. which shall re n-mince in loud tones the original sounds transniirlcil chctricaily without ths usual less of ilisrincincss 0r cieiirncss.

To this end the invention izmnprisms, gr n. erailly speaking, in ccnihiniitioi'i with ii infigns'a and an associated induction coil. an lll'lllillllll'i: plulie arranged inlcrinrly oi the coil and triinsvcrscly of its windings "with its Pl'OjCCtillg cnrls in close prcxiniily to the magnet pnlss, said armature plats being fulcrunieii in said ccils by non-Vibratory cushinning' niczrns so as is prevent distcrtinn of the viiiirziticn set up in the phitc by the inifluctivc ncixien of the electrical Waves or undulations in the coil currcnh while not inlerfcrring with the desired 'lrecrlcni of vihrirtioin ccm bincii with a sound-rcp10lucing diaphragm havilig vil'iriiticn transmitting cnnnection with the armature plate. This and. other fsiriures 0f the inventicn will. he described in the following spcciliciiiuinn and will be defined in thc claims herclu annexed.

In th s accompanying drawings 1 have, il lusl'ru-icri such details of ccnsuruction inil arriingeniicnc as are necessary to a ccnnplctc understanding of my aforesaid i1npr0vemerit, in which: A

Figure l is an elevation, piirlly in vortical section, showing an assemblage of parts embodying ihe present invention.

Figure 2 s'front elevation of the same in i plans ill right angles to the plane of Figure 1.

Figure 3 :1. plain View of rho cover 01' lid of the souncl has; partly i-ivninvecl in show this reprcduciiig diaphragm Figures 4 and. 5 are, respectively transwrsi: and longitudinal sections of the armslnrc plat e ini ninrml in the induction cnil.

l' i grnre i3 is a plain VlQW oi the arnnnfiure plain will: min form of cushioning: support, Flgilrhs T and 5 shcw, rcspciilzivi-il ifl in L hm zinc in cross section, another {UI'RllI LF inunt, nylhc cushioning support of the iirnnilurc philie.

igurcs l) and 10 are similar views of another nwrlilieaiion of the armature, plate. in the practice of the invention, accord ing to the specific (llllbfit'illlllttilll thereof i1 hislrritcrl in the ilrmvin 's, I emplcy a permanent; magnet 1, whose poles-{in this instance, prcviileil with inwardly projectinw' n): cnsions E3 and which are forked or grooved to Sllikiilli- 'idfl ciich pole of the magnet into parallel branches, WllUSB ends are in gums-p on in the ends cli the branches of thy nppcsrtc pnlc.

in the space 'l'crzneil by these gitnnyes in the opposing pclcs mounted. a spool i, having ii hcllnw nr flail; tubular r0re,,zrnd carrying a consirlcrnhlc length of line insuhitcol wirc coil :3, forming an induction coil in circuit will! the rci'iroducing circuit of i lli receiving set This spool l is arranged Willi its central opening or hollow core in alignment with the space separating the opposite poles of the nmgnet.

Within this hollow core of the induction coil and spool l, 5,-is mounted 2L transverse plate 6 oil niiigiietinzible material, such as soil; iron or the like. with its opposite ends projccting through Lhe rcil and in close prmLiiniLy to the pcles oi the magnet.

The mounting of ihis armature plate inside the coil is oi? Lhc utmost importance. At this point, my improvement consists in pruviding such ii supporl for the armature plate that it, is held thereby in proper rvhition to the coil and the nmgnet poles, while at the snare time its "vibration, due to the llldllliiliT-l iictipn n'l' theundulations or wiivcs in the current of the coil 5, shall not be distorted or marl-ml by the supporting connertiqn. There are scverzil forms 0 such supporting connection illustrated in the drawings but all embrace the use of an elastic support that will not transmit vibration and yet will allow (oniplctc frcciloin or vibration in The zu'nmlurc plain.

in lhe harms shown in Figures si. 5 'iind. (5 the ariniilnre plate 6 is provided with a row of spaced pin-fermions through which is drawn a strip of soft or elastic vulcanized rubber which is threadedthrougn from one side to the other so as to space the plate the rubber strip forming an elastic support the. current or bufi'er'normally holding the armature plate in its correct medial position, while allowing the plate to vibrate according to the nature oi the undulations or waves in passing through the induction coil.-

At one end, preferably for convenience the inner end, of the plate 6, there is secured a rod or wire 8, which is carried up and firmly secured to diaphragm 9, as shown at 8*, in order to transmit the vibration of the plate 6 to the'diaphragm' 9 and thereby reproduce sound waves corresponding to those originally transmitted by electrical waves to the apparatus. The joints at 8 and 8 with the armature plate and the diaphragm respectively, should be tight and nient illustrated, in order to make free from rattle and may be made eitherby soldering or mechanical connection. The sound box comprises a bottom member 10 and a top or cap 10 provided with a central opening 10 for the escape of the sound waves and for the insertion of a loud-speaking horn if desired. The two members of the sound box are secured together in any convenient fashion, as by screws, so as to clamp the peripheral or edge portion of the diaphragm between them with a circular space intervening between each face of the diaphragm and the adjacent :tace oi the sound box members. The vibration transmitting rod or wire 8 is preferably carried up through a hole in one arm of the magnet, according to the arrangethe apparatus compact as possible.

It will be observed that around the vibration-transmitting rod 8 is a rubber sleeve extending from the armature plate to the diaphragm. The object of this sleeve is to prevent excessive amplitude of vibration on the part of the relatively large diaphragm by intcrposing a non-vibratory buiier or damper which will not interfere with its normal vibration, but tends to prevent excessive ebound.

- In Figares? and 8 l'have shownamodified construction for supporting and cushioning the armature plate. In this case the armature plate, instead of being perforated, is notched midway of its opposite side edges and an elastic band 7 of rubber is stretched over-the plate to seat in these notches so as to form a transverse elastic fulhrnm for the plate corresponding in function to the strip 7, above described.

In Figures 9 and 10 the plate v6" is shown with two spaced perforations midway of the plate in which are inserted soft rubber buttons 7 forming an elastic fulcrum or support.

The preferred form of diaphragm has its central portion slightly bowed or cupped and the surrounding portion formed with annular concentric corrugations or waves to secure greater responsiveness to the transmitted vibrations. The armature plate is located in position of maximum responsiveness to the inductive action of the coil and also to the action of'the magnet poles, while at the same time with its elastic non-vibratory support there is no loss or distortion of vibration by transmission through any supporting means. tends to support the diaphragm in position and to yicldingly oppose movement of the diaphragm away from its medial position as Well as restoration to such position when it.

The elastic cushion ends of said plate projecting axially of the coil into juxtaposition with the respective poles of the magnet, a sound reproducing diaphragm and a metallic rod secured to one end of said plataand to the diaphragm to conduct vibration of the phragm.

2. A sound reproducing device embracing in combination an induction coil having a hollow. core, an armature plate mounted inside said hollow core upon an elastic nonvibratory cushion with its ends projecting beyond the sides of the coil, a magnet between whose poles said. coil is placed in position to locate the'ends of thev plate in close proximity to but out of contact with said armature plate, a sound-reproducing diaphragm and. means for transmitting vibrations of the armature to said diaphragm, and means for preventing excessive amplitude of vibration in the diaphragm interposed between the diaphragm and the armature. I

8. In a sound reproducing amplifier the combinationwith an induction coil having a hollow core and anarrnature plate in sorted transversely through said core and yieldingly fulcrumed therein at its medial point but out of contact therewith by vibration insulating supporting means tending to plate to the diav hold it in freedom of vibration in response to undulation in the electric current passing through said coil. l

4. In a sound reproducing amplifier, the combination with a' sound-reproducing diaphragm, of an armatureplate mounted inside an induction coil within the field of the poles of a magnet so as to be set in vibration by the 'oint inductive action of the magnet and of e current passing through the .coil, a rod connecting one end of the plate to said diaphra to transmit vibration of the plate, an a cushionin sleeve a cus 'oning and the diaaround said rod interposing resistance between phragm.

the plate medial position, while allowing it 5. A sound-reproducing amplifier embrac-' with a magnet, an

armature to said diaphragm.

In witness whereofll have subscribed the above specification.

ANGUS H. GIBSQN. 

